Projection systems are widely used today for home and business applications. One common example is the large screen projection television. Projection televisions allow for the viewing of an enlarged image by typically using one or more CRTs to produce red, green and blue color images that are transmitted through a projection lens system and superimposed on a viewing screen to display a full color picture. A typical projection lens system is located at the back of the television and projected on the back of the display screen, although there are also forward facing projection systems used for large screens.
The projection lens system is coupled to the CRT by using a projection coupler. The coupler is typically filled with a liquid that enhances the contrast of the picture and performs an important cooling function to dissipate the heat generated by each of the CRTs. An example of the coupler liquid commonly used today is a mixture of ethylene glycol and glycerin. The coupler is necessary in projection systems to cool the CRT lens face. An overheated CRT lens can lead to component failure and causes reduced contrast by distortion of the picture signal in the elevated temperature condition.
Past designs of couplers can cause a reduction of the contrast of the overall picture because of reflections of portions of the picture signals caused by the coupler inside walls. Projection couplers are typically made from a metallic substance and have smooth and shiny surfaces. Projection coupler manufacturers have attempted to address the lower contract caused by the reflections in the coupler by using different approaches. One such approach is coating the inner surface of the coupler contacting the fluid in the cooling chamber with a non-reflective substance. Conventional techniques include e-coat deposition that dips the coupler in a non-reflective substance. Another technique that is used is called anodizing. Anodizing dips the coupler in a chemical solution and applies electricity to the coupler that causes controlled corrosion that dulls the surface of the coupler. A third technique is stippling which causes small bumps to be created in the coupler wall. Stippling is caused by sand blasting the coupler or using particle bombardment. All these techniques cause increased manufacturing costs, and although they do help reduce the reflections of the picture signal caused by the coupler wall, they do not eliminate the problem. A cost effective additional technique is needed to reduce the extraneous projection optical signal reflections that reduce contrast.
The existence of the cooling liquid in the coupler formed cooling chamber can cause major damage to the projection system if it leaks into the system or surrounding devices. The coupler must also be stationary after it has been attached to the CRT faceplate to ensure proper alignment of the projection system. The coupler is typically attached to the CRT faceplate by a simple O-ring placed in a groove in the components to ensure a proper seal between the components. The O-ring placement between the coupler and CRT faceplate in the assembly process is typically performed by human workers. Sometimes the O-rings can turn slightly when being put in place thus creating a faulty seal that is difficult to detect. An improved seal design is needed in order to create a redundant seal so that if one of the seals is defective or is broken by sudden jarring, the second seal will remain in place. The improved seal design needs to be made with a minimum of manufacturing costs.
Small bubbles in the coolant in the coupler liquid chamber can be created either at the time of manufacture when the coupler is filled with the coolant or during the life of the product. The coupler will typically have an expansion chamber located outside the cooling chamber that allows the liquid to expand into the expansion chamber as the temperature of the liquid rises due to the heating of the CRT. The fill hole used to fill the cooling chamber formed by the coupler frame can also be in the expansion chamber. The continuous filling and receding of the liquid in the expansion chamber can cause air bubbles to be created. The air bubbles can act as tiny reflecting mirrors that can cause stray light signals that travel through the hole into the expansion chamber to be transmitted back into the cooling chamber containing the picture signal thus reducing contrast. The problem of the presence of these reflecting bubbles has not been previously addressed in other known designs. An improved coupler design is needed that will not dramatically increase manufacturing costs to solve the problems discussed above.